This invention relates to a method of heating or cooling the work surface of a laboratory work table and/or a laboratory hood. More particularly, this invention relates to heating of a work surface or hood by the insertion of a bladder system in the hood or the work surface. The use of a bladder system simplifies assembly, reduces labor involved, reduces cost, and also reduces the likelihood of leakage as compared to conventional systems. This invention is also related to the construction of such a bladder system.
Current laboratory tables and other surfaces are used to maintain a stable heated environment for the placement of specimens such as tissues, embryos and sperm, which require a steady temperature range. One example of this need is studying or working with mammalian cells which require a constant temperature of about 97xc2x0 F. These cells may be stored in incubators during their growth dormant stages and unused stages. These cells are removed from the incubator and taken to a controlled temperature work bench surface or work station for observation and/or manipulation. The work surface is made of stainless steel due to its anticorrosive nature and ability to maintain an evenly heated surface. Stainless steel is also durable and easy to clean.
The work surfaces are presently heated by one of two mechanisms. One involves the use of electric pads which are adhered to the underside of the work surface. The other involves the use of heated water which is circulated inside of the stainless steel work table structure.
The use of an electrically heated pad below the work surface has several problems in evenly heating the work surface. The electrically heated pads have a series of coils which heat various areas of the work surface and rely on heat sensors and relay systems which are embedded in the pads. The central area of the pads is the area where the heat control is most desirable. The stainless steel work surface has a tendency to lose a great deal of heat at its edges due to the fact that room temperature is less than the desired work surface temperature. Thus the colder edges draw heat away from the central areas of the work surface. This creates a temperature gradient across the work surface. The location of the temperature sensor maintains the desired temperature, but areas of the work surface which are spaced apart from the temperature sensor will have temperatures which may be several degrees lower than the desired temperature. The closer to the edges of the work surface, the lower the temperature.
For example, if the sensor is located in the middle of the pad and work surface, and the desired temperature is 97xc2x0 F., approximately halfway to the edge of the work surface, the temperature would be 95xc2x0 F., and at the edge of the work surface, the temperature would be 92xc2x0 F.
This variation in temperature would be maintained throughout the period of use of the work surface. When the sensor location temperature is reduced to 95xc2x0 F., which would be the trigger temperature for the temperature regulator to send an electrical surge through the coils to bring the surface temperature back to the desired temperature of 97xc2x0 F. An example of this is if the temperature of the center of the work table were to drop to 95xc2x0 F., the temperature of the intermediate areas of the table may drop to 92xc2x0 F., and the edges may drop to 90xc2x0 F. In that case, the regulator would send an electrical surge to reheat the pad which would reheat the center by 2xc2x0 to 95xc2x0 so as to satisfy the temperature requirements of the center of the pad, and then the regulator would shut off. The middle area of the work surface would also likely get a 2xc2x0 increase, as would the edges. Therefore, areas of the work surface will be less than the desired temperature throughout the operation of the work surface. Therefore, the aforesaid system is an undesirable manner of heating the work surface in question.
A more desirable solution to the problem is to use a heated fluid system wherein the fluid would be water, a gel, or some other flowable material. Currently employed heated water systems utilize a water pans which are adhered to the undersurface of the work surface. The water is heated with an external heated water bath which circulates water through the pan by means of an external heat pump. The water pan may be secured to the undersurface of the work surface by means on a silicone adhesive or by welding the pan to the undersurface of the work surface. Silicone adhesives are not desirable due to the fact that they will deteriorate and the water in the pan will then leak out of the pan. The welding option also has drawbacks which include scarring of the work surface by the welding temperatures, bowing of the work surface by the welding heat. The seals, whether by adhesives or welds, can also be deteriorated by contact with the heated water being circulated through the water pan. The present solutions to the problem of heating the work surface by means of circulating heated water through a pan attached to the undersurface of the work surface are thus flawed and undesirable.
An additional problem relating to the use of water pans relates to the use of optical instruments such as microscopes to observe the specimens on the work surface. When such optical instruments are used to observed the specimens, it will be necessary to provide light sources to illuminate the specimens, which light sources will be positioned below the work surface and the water pans. Thus, light pipes of some sort must be provided to pass light from the light sources through the water pans and the work surface. The current manner in which light is passed through the water pans, the water, and the work surface is by securing hollow tubes to the water pan and the work surface and passing the tubes through the heated water. Lenses are placed on the work surface at the top of the tubes. The securement of the hollow tubes may be by the use of adhesives or by welding. The same deterioration of the seal problems noted above occur when the heated water directly contacts the sealing adhesives and welds.
It would be desirable to provide a water heated system for controlling the temperature of a laboratory work surface, or other laboratory equipment which eliminates the problems which are incurred when the heating water directly contacts securement joints, such as adhesives or welds in the system.
This invention relates to the construction of a temperature controlled laboratory work surface system which is evenly heated or cooled by a fluid, such as water. The system of this invention utilizes a resilient bladder which is positioned adjacent to the work surface in a temperature transfer relationship with the work surface. The bladder is filled with a circulated heating or cooling fluid, such as water or some other fluid. The use of a bladder prevents the heating or cooling fluid from directly contacting the work surface.
The bladder may be made of pliable heat transfer materials such as rubber, polyvinyl, vinyl, Mylar, and urethanes; or the bladder may be formed from a metal such as copper or stainless steel. The bladder may be a unitary member, or may be composed of a series of interconnected members. A series of interconnected members allows the bladder to conform to several different patterns which may be required in different applications.
A template can be made from metal wiring which is capable of transferring radio wave frequencies (RF) to melt and seal the edges of the bladder or bladders. The template can be constructed so as to conform to the entire shape of the bladder, or it can be configured with different shapes which when sealed together in sequence will allow the bladder to vary in shape and size. One example of a bladder that can be used has a rectangular shape which measures from about twenty inches to about twenty eight inches in depth, and from about twenty four inches to about eighty inches in width. These length and depth dimensions will obviously depend on the size of the work surface being heated or cooled. The bladder can have a thickness which ranges between about one quarter inch to about six inches, again, depending on the size of the work table being heated or cooled. There can be at least one port into the bladder for the insertion of heating or cooling fluids thereinto. Preferably there will be a fluid inlet port and a fluid outlet port RF welded to or adhesively connected to the bladder. The spacing of the ports relative to each other should be such as to result in an even flow of water or air so as to result in an even distribution of the temperature-controlling fluid in the bladder. Variation of the thickness of the bladder material allows control of the bladder flexibility for various uses. The thickness of the bladder material will also determine the temperature transfer characteristics of the bladder when taken in conjunction with the heat transfer characteristics of the bladder material.
The bladder assembly is inserted between the underside of the work surface to be heated or cooled, and a lower bladder support pan on the lab table or work bench. The support pan serves to hold the bladder in place so as to maintain contact between the bladder and the work surface. The support pan also serves to retain the shape of the bladder and to prevent rupturing of the bladder.
Once properly positioned, the bladder can be heated or cooled by several different methods. One method is to use a heated or cooled air stream that is circulated through the bladder.
A second method involves the use of a hot or cold water pressure pump which circulates the temperature controlling water stream through the bladder.
A third method is to install a water-submersible electric coil inside of the bladder in order to heat water which may be circulated through the bladder or which may be sealed within the bladder.
A fourth method is to attach a heat source, such as a heating coil or a heating pad to the outside of the bladder, preferably to the undersurface of the outside of the bladder. The bladder may have a quiescent sealed fluid supply, or it may be provided with a circulating fluid supply. The heating coil or heating pad can heat the fluid from underneath the bladder, and the temperature of the fluid can be controlled by a sensor disposed inside of the bladder or outside of the bladder.
The temperature of the heating coil is preferably regulated by an external regulator which is operatively connected to the temperature sensor.
It is therefore an object of this invention to provide a laboratory table or work bench assembly which has a work surface which is heated or cooled by a fluid that is contained in a bladder which bladder is positioned inside of the table or work bench and is in heat transfer contact with the work surface.
It is another object of this invention to provide an assembly of the character described wherein the temperature-controlling media can be air, water or a flowable gel.
It is an additional object of this invention to provide a system of the character described wherein the temperature-controlling media is water, and the water is heated by a heating coil which is positioned inside or outside of the bladder.
It is another object of this invention to provide a system of the character described wherein the bladder is formed from a resilient material.